that's when the head of the u.s. anti-doping agency, travis tygart, pressed ahead and brought armstrong down. in his only interview, we spoke to tygart for "60 minutes." when you first heard that the u.s. department of justice was going to investigate whether criminal charges were appropriate in this case, what did you think of that? >> i thought it was absolutely appropriate. it was the right thing to do. federal taxpayers... close to $40 million were paid to this team to run what we now know was the most sophisticated and professionalized drug program the world has ever seen. >> pelley: after the criminal investigation was dropped, travis tygart pressed ahead and developed the evidence that cost armstrong his titles and resulted in his lifetime ban from sports. last month, tygart sent this letter to the u.s. attorney general urging him to join the fraud lawsuit. tygart wrote that armstrong's scheme was "one of the greatest frauds in the history of sport." he called armstrong's previous denials "cold, calculated lie